fullerenes

Fullerenes are a class of carbon allotropes consisting of hollow, closed cages made entirely of carbon. The most famous member is Buckminsterfullerene, or C60, a spherical molecule resembling a soccer ball. Other members include C70 and larger cages; many structures also form elongated or nested cages. Fullerenes can host atoms inside the cage (endohedral fullerenes) or be chemically functionalized on the outer surface, altering solubility and reactivity.

The C60 cage consists of 20 hexagons and 12 pentagons arranged in a truncated icosahedron, giving high symmetry and stability. This geometry underpins many of the cage’s distinctive properties. Fullerenes can form adducts with reagents on the surface, and some variants allow atoms to be trapped inside the cage.

Fullerenes were discovered in 1985 by Harold Kroto, Robert Curl, and Richard Smalley using laser vaporization of graphite. Their work earned the 1996 Nobel Prize in Chemistry. The name honors Buckminster Fuller, whose geodesic domes resemble the cage structure.

Production methods include laser ablation of graphite, arc-discharge in inert atmospheres, and various chemical routes to produce and separate individual fullerene species. Purification often requires chromatography and mass spectrometry.

Properties and applications: fullerenes are highly conjugated carbon systems with unique electronic characteristics, acting as electron acceptors in organic electronics and forming stable adducts with reagents. Endohedral fullerenes trap atoms inside the cage. Applications span materials science, photovoltaics, catalysis, and potential biomedical uses, though toxicity and solubility concerns necessitate careful handling. Research continues to expand functionalization and practical use.